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Old 08-02-05, 07:29 PM   #1
135crewchief
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What's the advantage of presta valves?

What's the advantage of presta valves?
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Old 08-02-05, 07:33 PM   #2
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Don't take this as gospel, but I remember reading somewhere that the smaller diameter of presta valves makes for less of a weak spot in the wheel 'cause of the smaller hole.

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Old 08-02-05, 08:09 PM   #3
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What's the advantage of presta valves?
Maybe a minor advantage - You don't have to work against a spring when you clip on the pump head.
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Old 08-02-05, 08:14 PM   #4
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you can get a smaller rim with a presta.
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Old 08-02-05, 08:52 PM   #5
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You don't have to carry a presta to schrader adapter....
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Old 08-02-05, 08:59 PM   #6
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You don't look like a noob.
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Old 08-02-05, 09:59 PM   #7
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They fit in that little presta size hole in the rim.




Was there a Monsieur Presta or a Mister Schrader?
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Old 08-03-05, 08:11 AM   #8
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My understanding is that the presta valve does a better job sealing with the higher pressures one sees on a bike, as opposed to automobiles, where the schrader standard comes from. Schrader valves are also a bit more susceptible to problems if dirt and gunk get under the plastic cap.
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Old 08-04-05, 07:32 PM   #9
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Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.

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Old 08-04-05, 09:03 PM   #10
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I thought the centrifical force actually 'forced' the sprung schrader valve to seal even tighter....
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Old 08-04-05, 09:50 PM   #11
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Nope, look at the direction that the valve moves to open and seal. The valve points towards the axle of the wheel. The spring pushes the valve towards the axle to seal. To open the valve, you push it outwards towards the outside of the wheel (towards the tyre), in the same direction centripedal force pushes the valve. Get enough RPMs spinning and you'll open the valve.
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Old 08-05-05, 08:06 AM   #12
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I've had a couple instances at Bonneville...
How sweet it would be to be able to drop that line in a conversation!
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Old 08-05-05, 11:02 AM   #13
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Quote:
Originally Posted by DannoXYZ
Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
I have that problem on my bicycle once in a while too. That's a helpful tip, thanks.
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Old 08-05-05, 01:36 PM   #14
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less likelihood of bursting tubes through over-enthusiastic use of air compressor to fill tires.




though this is less of an issue with these 100+ psi tubes...
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Old 08-05-05, 05:26 PM   #15
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Quote:
Originally Posted by DannoXYZ
Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
That's why Formula 1 cars use presta !

On a serious note, that's interesting. Never thought of it...
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Old 08-05-05, 06:08 PM   #16
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Quote:
Originally Posted by DannoXYZ
Nope, look at the direction that the valve moves to open and seal. The valve points towards the axle of the wheel. The spring pushes the valve towards the axle to seal. To open the valve, you push it outwards towards the outside of the wheel (towards the tyre), in the same direction centripedal force pushes the valve. Get enough RPMs spinning and you'll open the valve.
Yep, you're absolutely right... For some reason, I had imagined the valve sticking outward in a centrifuge!...stupid me...
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Old 08-06-05, 11:41 AM   #17
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Quote:
Originally Posted by DannoXYZ
Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
The next time I get my bike up to 185 mph I'll feel much more confident with my presta valves.

Al
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